The present disclosure relates to semiconductor light-emitting devices such as semiconductor laser diodes (LDs) and superluminescent diodes (SLDs) outputting light in a visible spectrum ranging from blue/violet to red.
A conventional semiconductor light-emitting device shown in Japanese Patent Publication No. 2004-289157 will be described with reference to FIG. 22. FIG. 22 is a perspective view illustrating the structure of a conventional semiconductor light-emitting device (a laser diode structure 100).
As shown in FIG. 22, an n-type contact layer 110, an n-type lower cladding layer 130, an n-type lower waveguide layer 140, a multiple quantum well (MQW) region 150, a p-type confinement layer 160, and a p-type upper waveguide layer 170 are sequentially formed on a substrate 101 such as a sapphire substrate.
An upper cladding layer 180 is formed on the portion of the p-type upper waveguide layer 170, which is located above an active region 155 of the MQW region 150. Portions of an insulating layer 185 face each other with the upper cladding layer 180 interposed therebetween.
A p-type electrode 190 made of metal is formed on the upper cladding layer 180 and on the insulating layer 185. On the other hand, an n-type electrode 120 made of metal is formed on an exposed region of the n-type contact layer 110.
The upper cladding layer 180 is not made of semiconductor but a transparent electrode material (e.g., conductive metal oxide). Specifically, with use of indium tin oxide (ITO), the upper cladding layer 180 has both of the functions as the cladding layer and a p-type electrode.
This structure provides a laser diode performing single-mode operation with largely reduced series resistance, while maintaining a high optical confinement coefficient.
Other than Japanese Patent Publication No. 2004-289157, Japanese Patent Publication No. 2006-41491, and Japanese Patent Publication No. 2010-21271 also show a semiconductor light-emitting device using a transparent electrode material.
Japanese Patent Publication No. 2006-41491 teaches using a cladding layer electrode made of ITO. Japanese Patent Publication No. 2010-21271 teaches using an upper transparent electrode film made of ITO.